This invention relates to the killing of unwanted insects and small animals, and more particularly to the use of an electric screen to accomplish this end.
Heretofore, chemicals have generally been used to eliminate insect and animal pests. While such chemical pesticides have been effective in killing pests, several deleterious side effects accompany their use. In outdoor fields such pesticides leave a chemical residue on plant life within the field. This chemical residue may be ingested when the plants are consumed, thereby affecting the health of animals higher in the food chain. In addition, most chemical pesticides must be reapplied at least once a year in order to assure the continued elimination of pests.
Pesticides spread in homes and other structures create a constant danger of poisoning to inhabitants. Even flea collars must be employed cautiously. At least several flea collars currently on the market utilize a nerve gas which has been known to affect people near the pet.
Furthermore insects are becoming more and more resistant to insecticides. Clearly, a nonchemical approach would add an important weapon in the arsenal of farmers and the like in the continuous war waged against pests.
The use of electrical screens to kill small animal life has been proposed in the prior art. U.S. Pat. No. 794,573 teaches an electrified screen apparatus for catching fish. The patent discloses a screen designed specifically for use in water and does not suggest a method of adapting it for use on dry land. Nor does the patent suggest a means of eliminating aquatic life from a large underwater area, because the only function of the apparatus is to catch fish.
U.S. Pat. Nos. 1,059,253, 2,278,538, and 3,077,050 disclose various electrical screens capable of destroying insect life. These devices have been designed to be mounted in a window or other opening to completely enclose an area. None of these patents suggest a method of eliminating insect life from a large open area such as an agricultural field.
Furthermore, these screens are not durable. Damage to even a small portion of the electrical screen devices mentioned above, particularly along one of their conductive edges, will eliminate electric power to the rest of the screen.
The present invention overcomes these problems in providing a durable electric screen for killing insects and small bugs. In the present invention, a set of weft strands, composed of alternating conductive strands and non-conductive strands are woven through a set of parallel warp strands, composed of electrically insulative material. To power the screen, some of the warp strands are replaced by busses, composed of non-conductive bases having separated conductive strips attached on opposite sides thereof. The pattern of the weaving is such that alternate conductive weft strands pass on opposite sides of the busses and contact the conductive strips on that side. Thus, when a voltage is applied across the conductive strips of each bus, the voltage appears across adjacent conductive weft strands.
The use of non-conductive weft strands between adjacent conductive warp strands adds to the durability of the present invention by eliminating the possibility of shorting which would occur if adjacent conducting warp strands were to touch. The use of a plurality of busses also adds to the durability of the present invention by allowing a large portion of the screen to be damaged or destroyed without affecting the electrical voltage in the remainder of the screen.
A screen as described above has many applications. It can be erected vertically around a field to kill entering insects.
If the spaces between conductors is made small, the screen could be used as a flea mat. The high voltage screen may be laid under a loosely woven mat of insulating material. Placed in the living or sleeping area of a pet, the high voltage mat would kill any fleas or other insects contacting it, and yet the loosely woven mat would protect the pet from injury.
A coarsely woven screen could be laid on the ground, on the deck of a ship, or around some object to be protected to kill animals having a size comparable to the grid dimension. An insulating layer under the screen may be employed to avoid any shorting on the surface beneath.
The screen of the present invention could also be used to remove pests from a field. Thus, a screen could be dragged behind a tractor over a field in order to stir up any insects and destroy them.
A relatively fine grid screen could be made in the form of a tape which may be laid on the floor in areas frequented by cockroaches, ants or other household insects.
When the screen is used to surround fields, or as a small animal pest killer, it is advantageous to employ an active power supply. Specifically, a small voltage is applied across the screen at all times. A sensing circuit produces a signal when the resistance of the screen is decreased, indicative of the presence of a pest. This signal triggers the application of a higher voltage across the screen which would kill the pest.
Obviously, both the power supply and the screen can be tailored to the type of pests to be killed.
Thus, the electric screen of the present invention has many advantages. Since materials for the screen are inexpensive and the method of manufacturing well known and efficient, the manufacturing cost is low. Since insulators run both directions and several busses are used, it has high durability. Furthermore, installation is easy and inexpensive and once installed, the cost of maintenance is low.